It is known that in making vehicle tires, for example for automobiles, that manufacture of a so-called carcass is first achieved by successively assembling several different components. In other words, the different carcass types included in a production range can be distinguished from one another depending on the presence thereon of the various accessory components and/or the typology of the accessory components themselves. By way of example, when carcasses for tubeless tires are to be produced, that is tires that in use do not require the presence of an inner tube, the main components can be considered to include a so-called inner liner that is a layer of elastomeric air-impervious material, a carcass ply, a pair of annular metal elements, commonly referred to as bead cores, around which the opposite ends of the carcass ply are folded, as well as a pair of sidewalls made of elastomeric material, extending over the carcass ply at laterally opposite positions. The accessory components may in turn comprise of one or more additional carcass plies, one or more reinforcing bands for overlying the carcass ply or plies at the areas turned up around the bead cores (chafer strips), and others.
A tire component of relevance to the present invention is the “toe guard”. A toe guard is an elongate strip of material, typically fabric, which is disposed in the bead area of the tire, that extends circumferentially around the inner surface of the bead area, and which comprises that portion of the tire which is in contact with the wheel rim. There are therefore two toe guards, per tire.
It is well known that the components of most pneumatic tire constructions must be assembled in a way which promotes good tire uniformity in order to provide proper tire performance. For example, a tread which “snakes” as it goes around the tire circumference will cause wobbling as the tire is operated. For example, a carcass ply which is lopsided (longer cords on one side of the tire than the other side) can cause a variety of tire nonuniformity problems including static imbalance and radial force variations. For example, a tire which is not meridionally symmetric (e.g., tread not centered between beads) can cause a variety of tire nonuniformity problems including couple imbalance, lateral force variations, and conicity. Therefore, in order to meet typical tire performance requirements, the tire industry generally expends considerable effort in producing tires with good uniformity.
Tire uniformity is generally considered to mean tire dimensions and mass distributions which are uniform and symmetric radially, laterally, circumferentially, and meridionally, thereby producing acceptable results for measurements of tire uniformity including static and dynamic balance, and also including radial force variation, lateral force variation, and tangential force variation as measured on tire uniformity machines which run the tire under load on a road wheel. Although certain degrees of tire nonuniformity can be corrected in post-assembly manufacturing (e.g., by grinding), and/or in use (e.g., applying balance weights to the rim of a tire/wheel assembly), it is preferable (and generally more efficient) to build-in tire uniformity as much as possible.
Typical tire building machines comprise a building drum, which is generally cylindrical and which has a diameter approximately equal to the bead diameter of the tire being built, around which the tire components are wrapped in successive layers including, for example, an innerliner, toe guards, one or more carcass plies, optional sidewall stiffeners and bead area inserts (e.g., apex), sidewalls and bead wire rings (beads). After this layering, the carcass ply ends are wrapped around the beads, the tire carcass is blown up into a toroidal shape, and the tread/belt package is applied. Finally the tire is completed using conventional techniques.
Certain tire building assembly lines use servers of various kinds for the purpose of securely holding flat materials, such as the tire innerliner, while it is being cut to size. Servers are commonly of the flat conveyor type, such as the one shown in British Patent No. 1,010,597 (Dunlop Rubber Company) or the conveyor and cutting system shown in U.S. Pat. No. 4,722,255 (Choate, et al.), wherein a continuous flat sheet of material is delivered upon a flat conveyor to a cutting knife. After severing, the material is removed to be placed upon the tire being built. Another such conveyor system is taught in U.S. Pat. No. 5,820,726 (Yoshida, et al.), incorporating a “transfer drum” element which feeds material to the conveyor system.
Drum-type servers, or so called “false drum” servers, are an alternative conveyor of flat or sheet tire materials that must be held securely while being cut. After being cut, the sheet material is moved to the tire under construction on the building drum. Generally such a false drum server comprises a horizontally disposed drum or cylinder that is able to rotate about its cylindrical axis. One particular false drum type server consists of a circular cylindrical drum that is hollow. The surface of the drum is perforated around most of its circumference, and air is pumped out of the drum in sufficient volume that the low pressure within the drum provides a suction adhering surface which can securely hold the flat or sheet materials that are being cut while being held on the server. When a flat sheet of material, such as tire innerliner, is placed on the perforated cylindrical part of the server, the pressure differential between the inside of the drum and the outside causes the flat material to adhere to the drum surface while the material undergoes a cutting operation.
The suction adhering part of the perforated drum type false drum server is its perforated cylindrical drum surface. The false drum server is typically of a much larger diameter than that of the building drum. (However, its diameter should be no less than the building drum.) Tire components, such as sheet rubber components, are measured to a required length on the false drum server, and then are cut before being transferred to the building drum. The tire components that are placed on the false drum server are held to the false drum server because the pressure differential across the perforated cylindrical surface makes the cylindrical surface into a suction adhering surface.
Typically, a tire component is placed on the false drum, cut to length, then transferred to the building drum, then the next component is placed on the false drum, cut to length, then transferred to the building drum. This process is repeated, as may be required, until all the component of a green tire carcass have been laid up on the building drum. When tire components are placed, in this manner, one at a time, from the false drum to the building drum, inaccuracies in the positions of the tire components can occur. And inaccuracies inevitably lead to non-uniformities in the final tire which, as discussed above, are undesirable.
Material is loaded onto the false drum, typically from roll stock, using a pickup unit. Any number of pickup units for picking up various tire components and placing them on the false drum are known. Two tire components of particular interest to the present invention are the inner liner and toe guards.